In this type of loom, the pneumatic system for insertion of the weft most frequently comprises an insertion nozzle, situated on one side of the loom, and numerous relay nozzles located along the axis of insertion, over the entire width of the loom. These relay nozzles, creating jets of air which complete the action of the insertion nozzle in order to pull and guide the weft thread until it reaches the other side of the machine, are distributed in groups each of N nozzles, each group of nozzles being supplied with compressed air by the same pneumatic pipe, the opening or closing of which is controlled by a solenoid valve actuated according to a predetermined sequence. Downstream of this solenoid valve, it is thus advisable to divide the flow of compressed air, corresponding to the consumption of all the relay nozzles of the group, into N partial flows, each of which will supply one of the relay nozzles of this group.
For applications of this type, one presently uses flow distributors in the form of parallelepipedal units of relatively slight thickness, with a central or lateral compressed air inlet and with a certain number of substantially aligned outlet passages on one of the faces of the parallelepipedal unit. An arrangement of this type favors the central outlet passage or passages, at the expense of the terminal outlet passages, a "baffle" effect being produced in the path of the compressed air between the inlet and the terminal outlet passages. Thus, the partial flows in the various outlet passages are not all equal and differences are also ascertained between the outlet passages for the response time on use and possibly for the pressure.